Severely deficient autobiographical memory (SDAM) in healthy adults: A new mnemonic syndrome
Abstract
Recollection of previously experienced events is a key element of human memory that entails recovery of spatial, perceptual, and mental state details. While deficits in this capacity in association with brain disease have serious functional consequences, little is known about individual differences in autobiographical memory (AM) in healthy individuals. Recently, healthy adults with highly superior autobiographical capacities have been identified (e.g., LePort, A.K., Mattfeld, A.T., Dickinson-Anson, H., Fallon, J.H., Stark, C.E., Kruggel, F., McGaugh, J.L., 2012. Behavioral and neuroanatomical investigation of Highly Superior Autobiographical Memory (HSAM). Neurobiol. Learn. Mem. 98(1), 78–92. doi: 10.1016/j.nlm.2012.05.002). Here we report data from three healthy, high functioning adults with the reverse pattern: lifelong severely deficient autobiographical memory (SDAM) with otherwise preserved cognitive function. Their self-reported selective inability to vividly recollect personally experienced events from a first-person perspective was corroborated by absence of functional magnetic resonance imaging (fMRI) and event-related potential (ERP) biomarkers associated with naturalistic and laboratory episodic recollection, as well as by behavioral evidence of impaired episodic retrieval, particularly for visual information. Yet learning and memory were otherwise intact, as long as these tasks could be accomplished by non-episodic processes. Thus these individuals function normally in day-to-day life, even though their past is experienced in the absence of recollection.
Authors
- Daniela J. Palombo3
- Claude Alain1
- Hedvig Söderlund1
- Wayne Khuu1
- Brian Levine5
Overview/Introduction
Methodology
- Participants: The study involved three individuals with SDAM, all of whom were healthy, high-functioning adults.
- Tests Conducted:
- Neuropsychological Tests: Assessed various cognitive abilities, including memory, attention, and motor skills.
- Behavioral Tests: Evaluated episodic memory through tasks that required recalling specific details of past events.
- Neuroimaging: Used functional magnetic resonance imaging (fMRI) and event-related potentials (ERP) to observe brain activity related to memory recall.
Key Findings
- Memory Performance: SDAM individuals showed a significant reduction in recalling episodic details, especially from childhood and teenage years. However, their ability to recognize and recall information in non-episodic tasks was intact.
- Neuroimaging Results: Brain scans revealed reduced activation in regions associated with autobiographical memory, particularly in areas linked to visual memory and self-projection through time.
- Hippocampal Asymmetry: There was a notable difference in the size of the right hippocampus compared to the left, which may contribute to the memory deficits observed in SDAM.
Implications
- Understanding Memory Variability: This study highlights the diversity in human memory capabilities and challenges the notion that vivid autobiographical memory is essential for normal functioning.
- Potential for New Treatments: Insights from SDAM could inform therapeutic approaches for memory-related conditions, emphasizing the role of non-episodic memory processes.
- Broader Impact: Recognizing and understanding SDAM can lead to greater awareness of memory diversity and reduce stigma associated with memory impairments.
Limitations
- Sample Size: The study was limited to three individuals, which may not fully represent the spectrum of SDAM experiences.
- Subjectivity in Memory Assessment: The reliance on self-reported memory experiences could introduce bias, as individuals may perceive and report their memory capabilities differently.